Compositions with Improved Adhesion to Low Surface Energy Substrates

Abstract

Acrylic-based pressure sensitive adhesives are modified with a telechelic hydrocarbon oligomer. The oligomer comprises a hydrocarbon polymer chain or backbone and a functional end group, e.g., an oligomer prepared from a mono hydroxyl polybutadiene polymer and toluene diisocyanate. The oligomer attaches to the acrylic backbone of the polymer as a pendant group and in a preferred embodiment, the oligomer is mixed with the PSA shortly before the PSA is coated.

Description

FIELD OF THE INVENTION[0001]This invention relates to adhesive compositions. In one aspect, the invention relates to acrylic pressure sensitive adhesive compositions while in another aspect, the invention relates to such compositions comprising telechelic compounds with improved adhesion to low surface energy substrates, e.g., nonpolar plastic films.BACKGROUND OF THE INVENTION[0002]The ability to adhere to low surface energy materials, e.g., materials with nonpolar surfaces such as polyethylene, polypropylene and other polyolefin films, is steadily increasing in importance due to the proliferation of such plastics in many components of manufactured products. While rubber-based pressure sensitive adhesive compositions (PSA compositions, or more simply PSA or PSAs) adhere well to low surface energy materials, these compositions often lack thermo-oxidative and ultra-violet (tV) light resistance. Acrylic-based PSA compositions, on the other hand, have excellent thermo-oxidative and V li...

AI Technical Summary

Benefits of technology

[0008]The PSA compositions of this invention exhibit not only good low surface energy adhesion, but they usually also exhibit at least one of good adhesion at low thicknesses, good high temperature cohesive strength, and formulation flexibility at the point of application. Regarding the formulation flexibility, this attribute of the invention allows more control over the physical properties of the PSA composition, including the amount of telechelic hydrocarbon oligomer incorporated into the composition, than is available from incorporating the oligomer directly into the backbone of the acrylic-based PSA (which must occur at the time the PSA is manufactured).

Problems solved by technology

While rubber-based pressure sensitive adhesive compositions (PSA compositions, or more simply PSA or PSAs) adhere well to low surface energy materials, these compositions often lack thermo-oxidative and ultra-violet (tV) light resistance.

However, acrylic-based PSAs in general lack good adhesion to low surface energy substrates due to the relatively high degree of polarity in the acrylic backbone,

Plasticizers, while very efficient at promoting viscous flow, compromise the cohesive strength of the PSA, especially at elevated temperatures, e.g., above 60 C.

While this method does improve the low surface energy adhesion of the PSA, the resulting acrylic-rubber based polymer still lacks good tack performance at low thicknesses.

This means that tackifiers are still necessary and as noted above, the addition of a tackifier adversely impacts the high temperature cohesion of the PSA.

Moreover, since the incorporation of the rubber must occur during the manufacture of the PSA, the flexibility to formulate a PSA composition at the point of application is lost.